The present invention relates to a matrix printer which includes a needle- or stylus-type printhead movable across a surface to be printed on. The invention relates particularly to the operation and construction of such a printhead for selective high-speed and high-quality type printing.
Generally speaking, matrix printers of the pin, needle or stylus type are usually constructed either to operate as high-speed printers or to compose high-quality characters, but at a rather slow printing speed. U.S. Pat. No. 4,159,882 proposes the vertical displacement of paper for obtaining high-quality printing in different passes. U.S. Pat. No. 4,010,835 proposes the use of two columns of styli, one being stationary on the head, the other one being displaceable. This printer can be used in two modes: low quality/high speed or high quality/low speed. High-speed operation finds respective two styli of the two columns horizontally aligned; high-quality operation is carried out in a staggered arrangement of the two columns so that, e.g., each vertical line is printed twice, once by each column but at a vertical displacement of the dots. However, one can readily see that this approach "beautifies" only vertical lines. Also, the paper advance is not matched to this type of operation.